Vehicles may use an engine oil system to lubricate and/or cool various components of an internal combustion engine during engine operation. The oil system for an engine supplies oil from a reservoir, often referred to as a sump, to various components of the engine requiring a supply of oil, such as bearings, hydraulic valve mechanisms, piston cooling jets, and piston ring contact areas of engine cylinders. However, if the engine is allowed to remain idle for extended periods of time moisture may enter the cylinders, possibly causing rust to develop, and the valve train parts (e.g., camshaft, valves, chains, piston rings) may become sticky. As such, when engines are planned to be stored for a long period of time, it is typical for vehicle operators to remove the spark plugs and inject oil inside the cylinders to keep them lubricated and to prevent rust buildup. Further, customers may elect to turn the engine over every few months in order to keep the valve train lubricated.
Plug-in hybrid electric vehicles (PHEVs) present a unique challenge to maintaining proper engine lubrication and overall engine upkeep, as PHEVs have the capability to operate significant distances in pure electric mode, without running the engine. For example, some customers may take mostly short trips, and may consistently plug in the vehicle between trips, such that the engine is almost never needed for battery charging. To avoid the issues associated with long periods of engine inactivity in PHEVs, the engine may be operated periodically even when it is not required for battery charging.
U.S. Pat. No. 8,479,849 teaches starting a vehicle engine to reduce effects of continued engine off operation, such as when a vehicle is consistently charged and the driver travels only a short distances. Further, the engine start may be delayed until selected conditions occur, such that the engine start and engine operation may be masked from the vehicle operator. However, the inventors herein have recognized potential issues with such a method. For example, starting and operating the engine to prevent potential degradation may reduce fuel economy and contribute to evaporative emissions. Additionally, while U.S. Pat. No. 8,479,849 teaches masking engine operation by starting the engine under select vehicle operating conditions, engine starting may still be noticeable, resulting in vehicle operator dissatisfaction. In one example, the vehicle operator may exert some control over when the engine may be activated responsive to an indication that engine operation is desired, however if the driver fails to activate the engine, the engine may still be activated without vehicle operator action.
Thus, the inventors herein have developed systems and methods to at least partially address the above issues. In one example, the issues described above may be addressed by a method including, propelling a motor vehicle by at least an internal combustion engine which rotates in a default direction by combusting fuel; and responsive to an indication of a vehicle engine-off duration greater than an engine-off threshold, spinning (rotating) the engine unfueled in a reverse direction opposite the default direction.
As one example, a vehicle may be configured to store fuel vapors in a fuel vapor canister configured in an evaporative emissions control system, and wherein spinning the engine unfueled in reverse may include routing air and fuel vapors to the fuel vapor canister. In some examples, air and fuel vapors may be further directed to the fuel vapor canister via the activation of an onboard pump configured to draw air and fuel vapors from the air intake system hydrocarbon trap in the intake manifold, and crankcase of the engine. During spinning the engine unfueled in reverse, an oil pump may be activated such that lubrication of the engine is performed. In this way, responsive to an indication of a vehicle-off duration greater than the engine-off threshold, the engine may be operated wherein lubrication of the engine may be performed, thereby preventing potential issues that may occur in the engine responsive to prolonged engine-off conditions. Furthermore, by activating the engine to spin unfueled in reverse, fuel economy may be improved as fueled engine operation is not performed to conduct the engine lubrication operation. Finally, by spinning the engine unfueled in reverse while concurrently activating an onboard pump, fuel vapors may be drawn to the fuel vapor canister, thereby preventing undesired evaporative emissions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.